Genes in higher organism are regulated through binding of regulatory molecules to regulatory sequences which may be in the gene or operatively linked to the gene. A variety of regulatory sequences are known. Among the gene regulatory molecules are steroids which typically bind receptor molecules to form a complex that can bind DNA to modulate gene expression. Androgens, glucocorticoids and estrogens are examples of steroids capable gene regulation through DNA sequences called androgen response element (ARE), glucocorticoid response element (GRE), and estrogen response element (ERE), respectively. Androgens form complexes with an androgen receptor (AR) to bind an ARE. Glucocorticoids form complexes with a glucocorticoid receptor (GR) to bind a GRE. Estrogens form complexes with an estrogen receptor (ER) to bind ERE. The AR, GR, and ER share a highly conserved DNA-binding domain. This domain, related to the classical Cys-2-His-2 zinc finger motifs, contains two modules of zinc coordinated by four cysteines.
AR signaling regulates for example normal prostate development and contributes to the progression of prostate cancer. Drug therapies that act to limit circulating androgen levels or directly antagonize ligand binding to AR initially slow prostate cancer growth but nearly all patients treated with such anti-androgen therapies will eventually develop hormone-refractory disease. Dysregulation of AR activity is thought to contribute to this transition. Up-regulation of AR mRNA, mutations in the AR itself, and ligand-less activation of AR through other signaling pathways contribute to this dysregulation. Direct antagonism of AR-DNA binding could inhibit androgen receptor activity in hormone-refractory conditions where androgen antagonists that target the ligand-binding pocket are ineffective.
ARE, GRE and ERE mediated gene regulation are involved in diseases including cancer. Inhibition of ARE-, GRE- and ERE-mediated gene regulation would be highly desirable in the treatment of diseases. Inhibiting ARE-, GRE- and ERE-mediated gene regulation requires, for example, selectively down-regulating the binding of natural regulators in a cell to the ARE, GRE and ERE. Inhibition of ARE and GRE mediated gene expression has been attempted through binding of small molecules to the ligand binding domains of the AR or GR to prevent binding of the AR or GR to AREs or GREs, or to prevent a transcriptionally active complex of AR or GR at AREs or GREs. Examples of such attempts are anti-androgen drugs (for example, flutamide and bicalutamide).
A different approach involves inhibiting the binding of AR, GR or ER to the ARE, GRE or ERE by occupying ARE, GRE or ERE with a molecule capable of specifically recognizing an ARE, GRE or ERE. Inhibition through specific binding of ARE, GRE or ERE would be an effective way to modulate gene expression, for example, to treat diseases like cancer. Inhibitors of ARE-, GRE-, and ERE-mediated gene regulation should be able to enter cells and to enter the nucleus of the cells. Such inhibitors should also be capable of accessing ARE, GRE and ERE sequences in the genome and they should not bind other sequences or molecules to a degree that would render them ineffective. Also, inhibitors should not accumulate in other organelles, for example lysosomes, to a degree that renders them ineffective.
Compounds capable of inhibiting ARE-, GRE- and ERE-mediated gene regulation would therefore be highly desirable. The present invention provides such compounds.